Small plot comparisons of phenology, yield, disease, and weed tolerance of three heritage and two newer cultivars of bread wheat under a high fertility organic regime in eastern Canada
A Report for the Old Wheats Web Site
(http://members.shaw.ca/oldwheat/)
Posted at www.dal.ca/~patriqui/wheat on 12 Feb. 2004
Moved to dp. biology.dal.ca/wheat on 29 Mar. 2005 |
Red Fife |
Sarah Evans1
David Patriquin1
Jennifer Scott2
1 Honours Biology student (SE) and Professor of Biology (DP) in the Biology Dept., Dalhousie University, Halifax, Nova Scotia, Canada B3H 4J1. (e-mail address for DP: patriqui@dal.ca)
2Farmer and researcher, Red Fox Farm,
Red Fox Farm, 178 Red Bank Rd., Centre Burlington, B0N 1E0. (jen@ns.sympatico.ca)
|
|
Abstract
Acadia |
Five cultivars of breadwheats that had shown promise in trials conducted by the Maritime Certified Organic Growers were grown in 1 x 1 m plots on a high fertility site with and without weeding. In minus-weed plots, grain yields of the heritage cultivars Acadia and Selkirk, but not of Red Fife, were equivalent to yields of the newer cultivars Coteau and Pollet. The heritage cultivars appeared to have some yield advantage in plus weed plots, probably because they grew in height faster than the newer cultivars. Differences in harvest index values between cultivars in minus weed plots reflect long term trends associated with plant breeding. Red Fife, which is one of the early progenitors of modern wheats, had the lowest harvest index (0.27) while the two newer cultivars had the highest harvest index values (0.50 for Coteau, 0.39 for Pollet); harvest index values of the heritage cultivars Selkirk (0.33) and Acadia (0.36) fell between that of Red Fife and the newer cultivars. Harvest index of Red Fife under highly weedy conditions (0.33) was much higher than under weed-free conditions (0.27) and Red Fife, with Selkirk, exhibited the highest yield under weedy conditions. All cultivars except Selkirk became heavily infested by powdery mildew. The infestation was effectively controlled by application of a seaweed/horsetail/garlic-based spray.
Purpose of this report, disclaimer, and request for feedback
This report was prepared by David Patriquin and posted on the web for the purpose of sharing preliminary conclusions from a field trial with the community of farmers, researchers and others who are actively involved in growing wheat organically. The experiment was conducted at one, high fertility site in a humid temperate region and it employed small plots that were set up and harvested manually. Thus the reported yields are likely well above those that would be obtained under typical farm conditions. We intend to publish the full study in a peer reviewed journal. Comments are sought and would be very much appreciated. Please send such feedback to David Patriquin. Please send queries about farmers' use of these breadwheats in the Maritimes to Jennifer Scott.
1. Introduction
Selkirk |
Five cultivars that had shown promise in trials of bread wheats conducted by the Maritime Certified Organic Growers Association in 1998-2000 [1] were compared for phonological development, yield, disease resistance and weed tolerance. They included three heritage cultivars (Red Fife, sometimes referred to as a landrace [2], brought to Canada from Poland in the 1800s, registered in 1904; Acadia, registered in 1952; Selkirk, registered in 1953) and two more recent cultivars (Coteau, released in North Dakota in 1978 and maintained by an organic farmer in North Dakota since then; CA Pollet, registered in 1992 and favored by organic farmers in Quebec). Red Fife was a common wheat in the Maritimes in the 1920s, Acadia and Selkirk in the 1950s [3]. The five cultivars were grown in small weeded and unweeded plots in a randomized complete block design with 5 replicates. No-competition plots, in which wheat was planted at very low density, were maintained for 36 days [4].
2.1 Phenological development
Wheat was planted May 15-17. It was harvested Aug 19-30 according to maturity. All cultivars reached the consecutive Zadok stages at close to the same times in both minus weed and plus weed plots except prior to 16 DAS (days after seeding) and after 74 DAS when there was some divergence between cultivars associated with different rates of germination and maturation respectively. The heritage cultivars germinated earlier than the newer varieties: 90% of final germination occurred at 12.2, 11.9, 11.7 DAS for Red Fife, Acadia, and Selkirk versus 12.3 and 12.8 DAS for Coteau and Pollet. The heritage cultivars also matured earlier than the newer varieties (102, 101 and 99 DAS for Red Fife, Selkirk, and Acadia versus 104 and 108 DAS for Coteau and Pollet). The average number of tillers at 40 days was lowest in Coteau (3.73) and highest in Acadia (4.67); others were in the range 4.20 - 4.47 per plant.
2.2 Early root growth, growth in height and light interception
We had expected that the heritage cultivars might have longer roots and/or higher root mass than the newer cultivars in the no-competition plots. However the only significant differences were for higher root mass in Pollet (2.1 g fresh weight per plant) compared to other cultivars (1.0-1.3 g/plant) and for longer roots in Coteau (20.5 cm) compared to Selkirk (16 cm). (Comparisons were made at 36 DAS.)
At mid-season (49 DAS) the heritage cultivars were taller (47-57 cm) than newer cultivars (40-42 cm) and effected greater light interception midway between rows (87-89%) than the newer cultivars (84-86%). Heights later in the season overlapped and were not significantly different (88-100 cm for the heritage cultivars; 89, 97 cm for the newer cultivars at 91 DAS).
2.3 Yields and harvest index in minus weed plots
In the minus weed plots, the heritage cultivars had higher total biomass or 'biological yield' (12.5 Ì 15 t/ha) than the newer cultivars (10, 12 t/ha) but lower harvest index values (Fig. 1). As a result, grain yields varied over a narrow range (4.5 - 5.2 t/ha) except for Red Fife (3.3 t/ha), which is explained by its very low harvest index. The heritage cultivars produced more straw (6.8 - 7.7 t/ha) than the newer cultivars (2.9 Ì 5.4 t/ha).
Fig. 1. Grain, straw, weed, biological (total) yields and harvest index values in minus weed (left) and plus weed (right) plots. CV=cultivar, Rf=Red Fife, Sk=Selkirk, Ac=Acadia, Ct=Coteau, Pt=Pollet; nc=no crop (weeds only). Harvest Index is ratio of grain yield-to-total crop (biological) yield; within the minus weed or plus weed group, harvest index values not sharing a common letter are significantly different (p=0.05). |
Coteau |
As much as 82% of the yield increase in cereals that was realized over the 20th century is attributed to breeding for higher harvest index (Gifford, cited in Evans [5]). According to Evans [5], harvest index of bread wheats "rose from 0.33 in 1950 to 0.46 in 1970 but declined with further increase in yield potential since then" (meaning that further increase was associated with increase in shoot weight).
Differences in harvest index values that we observed appear to reflect these long term trends. Red Fife, which is one of the early progenitors of modern wheats, had the lowest harvest index, the two newer cultivars had the highest harvest index values and harvest index values of the heritage cultivars Acadia and Selkirk fell between the values for Red Fife and the newer cultivars.
A higher harvest index results in a higher grain yield because a greater proportion of the total resources captured over the season ends up in the grains; there is usually a concomitant reduction in straw yield [5]. In our experiment, however, two of the heritage cultivars had grain yields equivalent to those of the newer cultivars but had higher, rather than lower straw yields. This was associated with higher total top biomass production ('biological yield') by the heritage cultivars, which is probably attributable to the heritage cultivars being taller and intercepting more light than the two newer cultivars for at least a portion of the growth cycle. It's possible that with closer row spacing, the newer cultivars would have out yielded the heritage cultivars. The site had exceptionally high fertility and moisture was generally adequate. The values of (crop + weed) biomass in plus weed plots were on average 1.4 times the values for crop biomass in the minus weed plots (Fig. 1). The percent light reaching the ground mid way between rows in the plus weed plots at day 56, when it reached the lowest values for the season, was 2.4 to 4.3% versus 11.3 to 15% in minus weed plots. Nitrate was reduced to lower levels in the plus weed plots than in the minus weed plots. These observations suggest that there was substantially greater use of light energy and soil nutrient resources in the plus weed plots than in the minus weed plots, i.e. that yield of wheat in the minus weed plots was limited by the capacity of the wheat plants (at the population level) to intercept light.
2.4 Yields and harvest index in plus weed plots
There were several hundred weed plants per square meter in the plus weed plots. The predominant species were lambsquarter, redroot pigweed, common ragweed and wormseed mustard.
High variability in crop yields between plots prevented firm conclusions being made about differences in weed competitiveness or tolerance of weeds between cultivars. However, overall, grain yields of the heritage cultivars in the plus weed plots were higher than those of the newer cultivars (Fig. 1). Ref Fife, with Selkirk, had the highest grain yield in the plus-weed plots. In contrast, Red Fife had the lowest grain yield in the minus weed plots. There was a statistically significant cultivar x weeding interaction for harvest index; harvest index of Red Fife was substantially higher and that of Selkirk slightly higher in the plus weed plots than in the minus weed plots; values for other cultivars in plus weed plots were similar to or lower than their values in the minus weed plots (Fig. 1).
2.5 Grain protein
Composite samples were analyzed for crude protein content:
| Sample ID | % crude protein
(dry basis) |
| Red Fife, minus weeds, Red Fox | 23.06 |
| Red Fife, plus weeds, Red Fox | 19.06 |
| Selkirk, minus weeds, Red Fox | 22.06 |
| Selkirk, plus weeds, Red Fox | 18.12 |
| Acadia, minus weeds, Red Fox | 19.81 |
| Acadia, plus weeds, Red Fox | 17.87 |
Coteau, minus weeds, Red Fox | 21.06 |
| Coteau, plus weeds, Red Fox | 17.93 |
| Pollett, minus weeds, Red Fox | 19.37 |
| Pollett, plus weeds, Red Fox | 16.37 |
| Acadia, plus weeds, different fertilizer, Red Fox | 16.81 |
| Red Fife, grown by FarmerA, 2003 | 22.25 |
| Acadia, grown by FarmerB, 2003 | 24.18 |
Samples from plus weed plots were consistently lower than the corresponding samples from minus weed plots.
2.6 Disease levels
A serious outbreak of powdery mildew occurred at mid-season. The outbreak was quickly controlled by applying a seaweed/horsetail/garlic-based spray. In cereals, this disease is described as severe only in the cooler, moist temperate regions. It is stimulated by excess nitrogen, and apparently was not a significant disease on cereals until late in the 19th century, which is attributed to rise in fertilizer use [6].
Pollet |
Prior to applying the spray, only a few of the Selkirk plants were infected, in contrast to the other cultivars which were heavily infected (Fig. 2). There was also a high incidence of Septoria glume blotch on mature heads. Both of these fungal diseases occurred more frequently in the minus weed plots than in plus weed plots, which was probably associated with higher levels of available nitrogen.
Fig. 2. Percentage of plants with powdery mildew at 45 days after seeding. |
Grain yields of the heritage cultivars Acadia and Selkirk, but not of Red Fife were equivalent to yields of the newer cultivars Coteau and Pollet under weed-free conditions.
The heritage cultivars had higher biological yields and higher straw yields than the newer culticars. However, Coteau and Pollet could exhibit grain yield advantages at higher densities and/or row spacing than were employed in this experiment (rows at 16.5 cm, 240 seeds/m2). The heritage cultivars appeared to have some advantage under highly weedy conditions, probably at least in part because they grew in height faster than the newer cultivars. Similar conclusions were reached by British researchers in a comparison of a traditional wheat cultivar with two modern cultivars [7]. Harvest index of Red Fife was significantly higher under highly weedy conditions than under weed-free conditions and Red Fife, with Selkirk, exhibited the highest yield under weedy conditions.
Organic growing conditions are likely more variable between fields and farms than are conventional growing conditions because of variable approaches to and success in, weed control and in provision of nutrients. Thus, it seems appropriate to have a wide range of cultivars available rather than recommending a specific cultivar for organic growers. All of the cultivars that we compared are probably suitable for at least one regime of organic growing, e.g. Pollet in high fertility regimes with a high level of weed control, Red Fife under weedy and possibly less fertile regimes. The high straw yield of the heritage cultivars may be particularly valuable in mixed farming systems.
1. Walker, D., Smith, A., Scott, J. and Fleischhaker, S. 2000. Evaluation of spring milling wheat cultivars at Speerville, Truro and Cherry Hill. Project #ARP 98005-2R. New Brunswick Dept. Agriculture, Fredericton, N.B., Canada.
2. Cassaday, K. ,Fowler,, C. Hersey, P.W. and Smale, M. 2001. Benefits from giving and receiving genetic resources: the case of wheat. PGR Newsletter No. 127. www.ipgri.cgiar.org/pgrnewsletter/article.asp?id_article=17&id_issue=127
3. Nass, H. Variety displacement study of spring wheats. In: Charlottetown Research Station (Agriculture Canada) 1971 Annual Report
4. Methods: see methods summary below
5. Evans, L.T. 1993. Crop Evolution, Adaptation and Yield. Cambridge University Press; Cambridge.
6. Schafer, J.F. 1987. Rusts, smuts and powdery mildew. In: Wheat and Wheat Improvement, 2nd ed. American Society of Agronomy, Madison, Wisconsin, pp 542-584.
7. Cosser, N.D., Gooding, M.J., Thompson, A.J. and Froud-Williams, R.J. 1997. Competitive ability and tolareance of organically grown wheat cultivars to natural weed infestations. Annals of Applied Biology 130: 523-535.
Summary of Methods
The experiment was conducted at Red Fox Farm, a small organic farm in Hants County, on the Minas Basin of the Bay of Fundy. The soil is a loam on which mixed vegetables had been grown for approximately 10 years, with regular sowing of red clover as a cover crop. Soil samples taken in the spring contained 4.7% organic matter and had a pH of 6.4. Ratings for P, K, Ca and Mg were E (excessive), H+ M-, M+ respectively.
To allow us to work with the small quantity of seed that we had for two of the cultivars, the experiment made use of small, 1 x 1 m plots. Plants in the outermost row or within 15 cm of the end of a row were excluded from sampling.
There were 12 treatments: numbers 1-5 were the five cultivars with weeds; 6-10 the five cultivars without weeds; number 11 was an unweeded, no-crop treatment (weeds only); number 12 was Acadia grown with crabmeal. The plots were laid out in a randomized complete block design with 5 replicates. (Treatment 12 was added to address a separate question which was whether growing Acadia with crab meal as a fertilizer would reduce disease incidence in comparison to Acadia grown with feathermeal fertilizer; this comparison is not commented on further. )
For each plot, fertilizer was applied to an area of 1.2 x 1.2 m and the soil turned over to a depth of 15 cm. Wheat was planted in the central 1 x 1 m area in furrows of 2.5 cm depth in 7 rows spaced 16.5 cm apart, with 40 seeds per row (240 seeds per m2). The fertilizer was feathermeal (9-0-0) applied to provide 69 kg/ha of supplemental N except for treatment 12 in which crab meal (5-2-6) was applied to provide the same level of supplementary N. No weeding was conducted on the plots with weeds; minus weed plots were manually weeded until canopy closure.
Germination was monitored daily for 7 days from the first seed emergence. Crop heights, weed heights and Zadok development stage were observed at approximately weekly intervals. Measurements of light extinction were made weekly. Electrical conductivity was measured on soil samples taken at planting, midseason and harvest; values were converted to nitrate using a previously observed relationship between nitrate and electrical conductivity for this site. At mid-season and maturity 70 cm sections of a single row in each plot were harvested for determination of crop and weed biomass and yield components. The harvest index was calculated as: 100 x (grain dry weight)/(dry weight of all aboveground parts).
Analysis of crude protein was conducted by A&L Labs, London, Ontario; for these analyses, all grains harvested from a treatment were combined and a single subsample analysed.
No-competition plots were set up adjacent to the weeded plots in four of the blocks. The same variety of wheat was planted in these plots as in the adjacent plots, but at wide spacing. The purpose of these plots was to characterize early belowground growth in the absence of either intra- or inter-specific competition. These plots were maintained for only 28 days. Observations, made on plants removed at 7 and 27 days, included maximum root length and root fresh weight.
|